1. Field of the Invention
The present invention in a broad aspect relates to analytical tools for monitoring electrochemical deposition (ECD) solutions, and more specifically to a process analyzer comprising microelectrodes for composition analysis of various metal electroplating solutions.
2. Related Art
Conventional ECD process analyzers use rotating disk electrodes (RDEs), for providing a well-defined flow of ECD solution towards the surface of such rotating disk electrodes, so as to provide stronger analytical signals (for example, the plating current).
When a rotating disk electrode rotates in a metal electroplating solution, it generates a flow pattern akin to a vortex that sucks the solution as well as analyte therein toward it. The layer of solution that is immediately adjacent to the surface of the rotating disk electrode behaves as if it were “stuck” to such electrode, i.e., while the bulk of the metal electroplating solution is being stirred vigorously by the rotating disk electrode, this thin layer of solution manages to cling to the surface of the electrode. Therefore, this thin layer of solution is generally referred to as “the stagnant layer” or “the boundary layer.”
The metal electroplating solution and the analyte therein are conveyed to the surface of the rotating disk electrode by two types of motions: (1) the vortex flow generated by rotation of the RDE continuously brings fresh solution and analyte therein to the outer edge of the stagnant layer; and (2) the solution and analyte therein at the outer edge of the stagnant layer move across such stagnant layer via molecular diffusion. Therefore, the thinner the stagnant layer, the faster the solution and analyte therein can diffuse across it and reach the surface of the rotating disk electrode, and the higher the electric current measured by the RDE.
For generating a sufficiently thin stagnant layer, the RDE is generally operated at a rotating speed above 800 rpm, rendering such RDE prone to mechanical breakdown after continuous operation.
Moreover, the conventional RDE usually has a diameter of from about 1.5 mm to about 10 mm, in order to ensure structural integrity and reliability at such high rotating speed. Therefore, an ECD process analyzer that comprises a plurality of such conventional rotating disk electrodes is inevitable bulky in size.
Finally, when using such bulky ECD process analyzer, a large volume of sample metal electroplating solution has to be used in order to obtain sufficient analytical signals, generating a large amount of waste solution.
It would therefore be a significant advance in the art, and is accordingly an object of the present invention, to provide an ECD process analyzer comprising electrodes that are resistant to mechanical breakdown, small in size, and generating minimum amount of waste solution during solution analysis.
It is another object of the present invention to provide an automated analytical platform that comprises multiple analysis modules suitable for various kinds of fluidic analyses, preferably including at least one ECD process analyzer as described hereinabove.
Other objects and advantages will be more fully apparent from the ensuring disclosure and appended claims.